More than 40 experts have written to the government’s public health agency to oppose its tie-up with a charity funded by the alcohol industry for the Drink Free Days campaign.

The letter, written before the campaign was launched this week, said it “will significantly damage the credibility of Public Health England”.

Martin McKee, a professor of European public health at the London School of Hygiene and Tropical Medicine and one of the 46 signatories to the letter, accused PHE of giving unwarranted credibility to the drinks industry.

It came as Prof Ian Gilmore, a PHE senior adviser on alcohol, resigned over the agency’s refusal to scrap the tie-up with Drinkaware.

Speaking on Thursday, McKee told BBC Radio 4’s Today programme: “The tie-up with Public Health England does give the alcohol industry a lot of credibility. It says we are part of the solution when clearly they are not.”

He said the campaign was aimed at “promoting something that is not particularly effective and more importantly, it is diverting attention from the things that are effective”.

According to the BBC, the letter to PHE said: “Industry-funded messages and social marketing campaigns should not be a substitute for publicly funded campaigns providing independent and evidence-based information.”

Earlier this week, Gilmore had said his concerns were being ignored and his role was being undermined. Prof John Britton, who advises PHE on tobacco, also threatened to resign but has not done so.

PHE said it was “steadfast in its ambition to reduce the harms that drinking too much alcohol can cause”.

McKee said: “I think Drinkaware do know that many of these messages [about drink-free days] are ineffective.”

He added that public health experts favoured other measures such as minimum unit pricing. “The rest of the health community unanimously is saying this is a good idea and should be introduced in England. They [Drinkaware] really stand out as the outliers in not advocating for that,” he said.

McKee said the tie-up was part of a worrying trend of industry influence on public health policy.

“Public Health England needs to look more broadly at its relationship with industries that produce potentially harmful substances. There is a pattern emerging where they are in discussion with other companies that are producing damaging things,” he said.

“They are creating a climate where other people feel encouraged to do this. Look at the potential tie-up between British American Tobacco and public health in Birmingham recently, which again produced incredulity. This takes us into an area which we refer to as corporate or commercial determinants of health – the role of large corporations in shaping the agenda and in influencing policy.”

Prof John Newton, the director of health improvement at PHE, told Today: “We have ensured that the Drinkaware campaign, which would otherwise possibly be dominated by advice from the industry, is now following our advice and is more likely to improve the health of the population than if we hadn’t got involved.

“We didn’t make a mistake. We are very sorry that colleagues disagree with us on this topic. Public Health England’s independence has not been damaged one iota by this.

“Drinkaware already has 10m visits a year to their website from people who drink and who want help. We see that as an opportunity to get messages out to people who are drinking.”

A PHE spokesperson later said it hoped to persuade Gilmore to rescind his resignation.

A Drinkaware spokeswoman insisted the charity was independent and did not speak on behalf of the alcohol industry.

“Our commitment to helping people make informed choices about alcohol is unswerving and to suggest otherwise is to wholly and wilfully misrepresent the charity and its aims,” she said.

• This article was amended on 13 September 2018. An earlier version quoted Professor McKee referring to the “potential tie-up between British American Tobacco and Public Health in Birmingham”. That has been changed to “public health in Birmingham” to make it clear that the potential relationship is with Birmingham city council, not Public Health England.